In the field of recording of information signals, a variety of disc-shaped recording media, such as optical discs or magneto-optical discs, utilizing optical or magneto-optical signal recording/reproducing methods, have been developed and are present on the market. These planar disc-shaped recording media include but not limit to read-only-memory (ROM) type recording media, such as compact discs (CDs) of various kinds, and DVD discs of various kinds, wherein video and audio materials are stored either compressed or uncompressed. These various types of CDs, VCDs, DVDR, or DVDs are included by the term optical disc(s).
With an optical disc recording/reproducing apparatus, the rotational speed of a spindle of a disc driving device adapted for rotating the optical disc is controlled for rotating the optical disc at either a constant angular velocity (CAV) or the much more common constant linear velocity (CLV) for a constant bit error rate (BER). The optical disc rotated by the disc driving device is irradiated with a laser light from a semiconductor laser enclosed within the optical head, and the laser light reflected back from the optical disc is detected by a photodetector enclosed within the optical head for reading the information from the optical disc.
In order that the laser light radiated from the semiconductor laser may be correctly converged on the signal recording surface of the disc and is able to follow the recording track formed on the optical disc in the correct manner, the optical head also performs focusing control and tracking control for the laser light on the basis of the detected output of the photodetector.
A single-sided, single (reflective) layer optical disc comprises several layers, the first of which is a layer of a clear layer made of polycarbonate or a similarly serving material. The polycarbonate layer forms the basic substrate for the optical disc. The next layer is a thin layer of a reflective metal film disposed on the upper side of the polycarbonate first layer. This reflective layer is the recording media in the optical disc made up of reflective islands and pits. Above the metal layer is a label layer, which often consists of silk-screened ink and a protective lacquer coat, and forms the top surface of the optical disc. An aperture is used to position and spin the optical disc in recording and playback operations. It should be noted that the reflective metal layer and the label layer are generally very thin in comparison with the polycarbonate substrate layer.
A bottom view of the reflective layer of a single-sided, single layer optical disc shows what appears to be a plurality of rings. These rings are actually a single, tightly-wound spiral. The single spiral is located on the top surface of the metallic reflective layer, but is visible only from the lower side, through the clear polycarbonate substrate.
To read information contained on a single-sided, single layer optical disc, the optical disc is placed in a player and rotated about the disc central axis; the disc central axis coinciding with the center of the disc aperture. A laser beam is directed to illuminate precisely-selected portions of the spiral. The beam is typically directed from under the optical disc. More particularly, the laser beam passes through the clear polycarbonate substrate of the optical disc and travels to the reflective metal layer.
Information is recorded onto optical discs by forming small pits and lands, at desired locations along the single spiral. During playback, the pits and lands are “read” by detecting laser light reflected from these pits and lands. Upon the laser beam striking the reflective metal layer, the laser beam illuminates information-carrying indentations located thereupon. In turn, portions of the laser beam are reflected back to an optical sensor, which produces an electrical output that varies in accordance with the reflected laser beam.
A single-sided, single layer optical disc generally includes three areas at the beginning of the spiral: a lead-in area, a volume structure area, and a file structure area. The three areas are normally called the table of contents of the optical disc. The remaining spiral is used for saving contents such as movies.
Other types of optical discs such as single-sided, double layer; double-sided, double layer optical discs operate with a similar principle. A single-sided, double layer optical disc, for example, includes two reflective layers, both read from the same side. As such, the capacity of a single-sided, double layer optical disc is almost twice of a single-sided, single layer optical disc.
Assembly lines for the production of optical discs, e.g., DVDs, are well known and established. Considering the great proliferation of the titles of DVDs, there is a concern that a non-conforming (wrongly subject/titled) DVD will find itself in the wrong production line even though discs are inspected for content that the correct disc is being used for a particular order. However, despite precautions, if an incorrect disc does make it's way to the end of the production line and is incorrectly shipped to a customer in a wrong shipping container with a wrong title, the disc may be viewed by a customer with age or mental sensitivities, e.g., a child or a religious person, unintentionally viewing a optical disc intended  for an adult audience, e.g., having offensive violence or language content for that particular viewer.
Prior art precautions have included having the assembly machine place the incorrect disc into the package and then rejecting the package at the outfeed of the machine. However there is still a possibility that the package machine operators could by mistake reintroduce the rejected package into the acceptable packaged product line, i.e., to contaminate the product line. As such, once there is a determination of the disc being improper, the disc, at a minimum, should be made unplayable on a consumer's playback machine.
In this respect, the total destruction of data including the contents and the table of contents on an optical disc as shown in U.S. Pat. Nos. 6,039,637, 6,189,446 and 6,338,933 certainly prevents a non-conforming optical disc from reaching a customer. However, the total destruction renders future determination of the root cause of the occurrence of the non-conforming optical discs difficult if not impossible. Thus, it is desirable to provide apparatus and method therefor for assuring that the title or other identification label of an optical disc conforms with the title or other identification label of its shipping container, and if not, that the optical disc be made unplayable on the playback machine of a unintended user without totally destroying the non-conforming discs. An unintended user as used herein means a user receiving an optical disk with a subject and/or title different from what the user is expecting.